1. Technical Field
The present disclosure relates to hot-work mold steel for die casting and a method of manufacturing the same, and more particularly to hot-work mold steel having a long life cycle with superior hardenability and nitriding characteristics, suitable for use in the production of vehicle parts, and a method of manufacturing the same.
2. Description of the Related Art
Alloy elements for hot-work mold steel include carbon, chromium, silicon, nickel, molybdenum, manganese, vanadium and cobalt, in addition to iron. Hot-work mold steel including such alloy elements may exhibit superior mechanical properties even at high temperatures, and is thus used for the production of extrusion dies, forging molds and die-casting molds, which require special mechanical strength at high processing temperatures.
Hot-work mold steel and steel products manufactured using the same, for example, molds such as die-casting dies, are applicable to a variety of technical processes. These applications require a uniform temperature on the entire surface of the mold so as to impart uniform quality to molded products, high thermal conductivity for sufficient dissipation of the generated heat during subsequent processing, and high thermal wear resistance.
Furthermore, resistance to heat check and melt-out of hot-work mold steel is directly associated with the life cycle of a hot-work mold, and thus, in order to maximize such properties, surface treatment including nitriding is performed. Since the depth to which introduced nitrogen penetrates the surface of the mold through nitriding and the extent of production of a nitrogen compound layer are directly associated with the chemical composition of a mold, resistance to heat check and melt-out due to nitriding is also directly affected by the chemical composition.
In addition to the above properties, hardenability of the hot-work mold steel is also regarded as important. As hardenability increases, a more homogeneous and robust steel structure may be obtained over a wider temperature range under the same heat-treatment conditions, and these same conditions may also be applied to relatively large molds. Hence, when hot-work mold steel has high hardenability, it is possible to manufacture more robust molds and molds of various sizes.
With the recent trends towards environmental friendliness and high fuel efficiency in the automotive industry, the use of lightweight non-iron metal is increasing and the demand for hot-work mold steel for die casting is also increasing. Since conventional techniques make it difficult to impart sufficient hardenability and nitriding characteristics to hot-work mold steel for die casting having a long life cycle, the development of hot-work mold steel that may overcome these problems is needed.